The treatment of acute lung failure, acute lung injury (ALI), and acute respiratory distress syndrome (ARDS) is still one of the key problems in the treatment of severely ill patients in the intensive care unit. Despite intensive research over the past two decades, the negative implications of respiratory insufficiency are still affecting both the short and long term outcome of the patient. While different ventilator strategies have been designed to treat the oxygenation disorder and to protect the lungs from ventilator induced lung injury, additional therapeutic options have been evaluated.
Dynamic body positioning (kinetic or axial rotation therapy) was first described by Bryan in 1974. This technique is known to open atelectasis and to improve lung function, particularly arterial oxygenation in patients with ALI and ARDS. Since kinetic rotation therapy is a non-invasive, relatively inexpensive method, and with very limited side effects, it can even be used prophylactically in patients whose overall health condition or severity of injury predispose them to lung injury and ARDS. It could be shown that the rate of pneumonia and pulmonary complications can be reduced while survival increases if kinetic rotation therapy is started early on in the course of a ventilator treatment. This therapeutic approach may reduce the invasiveness of mechanical ventilation (i.e., airway pressures and tidal volumes), the time on mechanical ventilation, and the length of stay on an intensive care unit.
Kinetic rotation therapy in the sense of some exemplary embodiments of the present invention can be applied by use of specialized rotation beds which can be used in a continuous or a discontinuous mode with rests at any desired angle for a predetermined period of time. Examples of such beds are described in whole or in part in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. Nos. 4,638,516; 4,763,643; 5,299,334; 4,947,496; 4,730,606; 4,868,937; 6,874,181; 6,112,349; 6,108,838; 6,671,905; 6,566,833; 6,715,169; 7,017,211, 6,934,986; 6,732,390; 6,728,983; 6,701,553; 7,137,160; 6,609,260; 6,862,761; 6,282,736; 6,526,610; 6,499,160; 6,691,347; and 6,862,759. Examples of such beds are also described in whole or in part in the following U.S. patent Publications, all of which are incorporated herein by reference: 20060162076 and 20060037141. A rotation bed that is suitable for adaptation with some exemplary embodiments of the present invention is presently commercialized under the trademark “ROTOPRONE”, commercially available from Kinetics Concepts, Inc., of San Antonio, Tex. (“KCI”).
Kinetic rotation therapy in the sense of some exemplary embodiments of the present invention can be applied by use of specialized beds which comprise air cushions provided underneath the patient. Examples of such beds are described in whole or in part in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. Nos. 5,142,719; 5,003,654; 5,603,133; 6,282,737; 5,152,021; 5,802,645; and 6,163,908. A rotation bed that is suitable for adaptation with some exemplary embodiments of the present invention is presently commercialized under the trademark “BIODYNE”, commercially available from KCI.
A general effect of axial rotation in respiratory insufficiency is the redistribution and mobilization of both intra-bronchial fluid (mucus) and interstitial fluid from the lower (dependent) to the upper (non-dependent) lung areas, which will finally lead to an improved matching of local ventilation and perfusion, also known as V/Q match. As a consequence, oxygenation increases while intra-pulmonary shunt decreases. Lymph flow from the thorax is enhanced by rotating the patient. In addition, kinetic rotation therapy promotes the recruitment of previously collapsed lung areas, thus reducing the amount of atelectasis, at identical or even lower airway pressures. At the same time, now-opened lung areas are protected from the shear stress typically caused by the repetitive opening and closing of collapse-prone alveoli in the dependent lung zones. From H. C. Pape, et al.: “Is early kinetic positioning beneficial for pulmonary function in multiple trauma patients?”, Injury, Vol. 29, No. 3, pp. 219-225, 1998 it is known to use the kinetic rotation therapy which involves a continuous axial rotation of the patient on a rotation bed. See also Bein T, et al. Clinical Intensive Care 1995. Bein T, et al. Intensive Care Med 1998. Bein T, et al. Clinical Intensive Care 2000.
It has been found that the kinetic rotation therapy improves the oxygenation in patients with impaired pulmonary function and with post-traumatic pulmonary insufficiency and ARDS.
However, because the kinetic rotation therapy requires a specially designed rotation bed, it has not been found yet that kinetic rotation therapy justifies a broad employment. Further, kinetic rotation therapy has been utilized with standardized treatment parameters, typically equal rotation from greater than 45 degrees to one side to greater than 45 degrees to the other side, and 15 minute cycle times. These rotation parameters are rarely altered in practice due to a lack of conjoint ventilation effectiveness and rotation activity information. Similarly, the lack of conjoint information hampers practitioners from taking advantage of the beneficial effects of kinetic rotation therapy by reducing the aggressiveness of mechanical ventilation parameters employed to treat a rotated patient.
Since positioning therapies such as kinetic rotation therapy and proning are lung-protective and improve oxygenation, ventilation drive parameters need to be adjusted downward in order take full advantage of the benefits of the positioning therapies. The question is how to do so effectively. Prior techniques have viewed ventilation and positioning as separate therapies to be independently titrated to patient needs and responses. For example, a great deal of literature exists on how to optimize PEEP levels based on lung mechanics data, imaging information, patient diagnoses, and other information. None of these methods, though, have recognized the role of positioning therapies in influencing the same measures used to tune ventilation. Similarly, positioning therapies have typically been prescribed upon patient diagnoses without regard to specific information about effectiveness of ventilation.
U.S. application Ser. No. 10/594,400, filed Sep. 26, 2006, and PCT Application No. PCT/US2005/010741, filed Mar. 29, 2005 (published as WO 2005/094369), both of which are incorporated herein by reference, describe methods of combining information from both kinetic and ventilation therapies to allow conjoint analysis of the interaction of each on the other. The references disclose the use of various types of ventilation status information, including respirator measures, hemodynamic measures, and imaging data, in optimizing the two therapies in question.
Instead of using the rotation beds described above for automatically turning and proning a patient to treat ARDS and other lung conditions, some institutions use manual turning of the patient to achieve a similar result. However, there is little guidance to such institutions on when to turn the patient, how long to leave the patient prone, whether leaving the patient at a rotational angle is beneficial, or whether adding a change in pitch is appropriate.
Various methods for the automated control of ventilation are known to those of skill in the art. Examples of such methods which are suitable for use with exemplary embodiments of the present invention are described in Laubscher et al., “An Adaptive Lung Ventilation Controller,” IEEE Transactions on Biomedical Engineering, Vol. 41, No. 1, pp. 51-59, 1994 (“Laubscher-1”), and Laubscher et al., “Automatic Selection of Tidal Volume, Respiratory Frequency and Minute Ventilation in Intubated ICU Patients as Startup Procedure for Closed-Loop Controlled Ventilation,” Int. J. Clinical Monitoring and Computing, 11:19-30, 1994 (“Laubscher-2”), both of which are incorporated herein by reference. Laubscher-1 describes a closed loop ventilation method called Adaptive Lung Ventilation (ALV), which is based on a pressure controlled ventilation mode suitable for paralyzed, as well as spontaneously breathing, subjects. As explained in Laubscher-1, the clinician enters a desired gross alveolar ventilation (V′gA in 1/min), and the ALV controller tries to achieve this goal by automatic adjustment of mechanical rate and inspiratory pressure level. The adjustments are based on measurements of the patient's lung mechanics and series dead space. Laubscher-2 describes a computerized method for automatically selecting startup settings for closed loop mechanical ventilation. An automated ventilation control algorithm that is suitable for adaptation with some exemplary embodiments of the present invention is presently commercialized under the trademark “Adaptive Support Ventilation” or “ASV”, commercially available from Hamilton Medical, Inc., of Reno, Nev.
Other methods of automated ventilation control which are suitable for use with exemplary embodiments of the present invention are described in U.S. Pat. No. 4,986,268 (“Tehrani”), which is incorporated herein by reference. Tehrani describes a method for automatically controlling a ventilator in which the ventilation and breathing frequency requirements of a patient are determined from measurements of several parameters, including the air viscosity factor of the patient's lungs, the barometric pressure, the lung elastance factor of the patient, measured levels of carbon dioxide and oxygen of the patient, and the metabolic rate ratio of the patient.
One problem associated with hospitalized and particularly ventilated patients is pneumonia. The incidence of these pneumonias has been estimated at 9-40% (Safdar et al 2005). One cause of these pneumonias is foreign matter, and particularly infectious matter, entering the lungs. In the case of the ventilated patient this matter enters the lungs around, as well as through, the endotracheal tube used to ventilate the patient. This is generally referred to as ventilator-associated pneumonia.
In addition to ventilator-associated pneumonia, non-ventilated patients are also prone to pneumonia. In these patients aspiration of fluids is often the cause of the pneumonia. This is called aspiration pneumonia. The fluid aspirated can be tracheal, oral, and/or gastric. Small studies by Garvey et al. (1989) and Apte et al. (1992) both show approximately 50% of these pneumonias could be traced to organisms of gastric origin.
Increasingly rigorous and robust studies have shown the enormous cost, morbidity, and mortality of infections acquired in the intensive care unit in general and of ventilator-associated pneumonia in particular (Jackson and Shorr 2006).
Any problems or shortcomings enumerated in the foregoing are not intended to be exhaustive but rather are among many that tend to impair the effectiveness of previously known techniques. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that apparatuses and methods appearing in the art have not been altogether satisfactory and that a need exists for the techniques disclosed herein.